Communication devices such as wireless devices are also known as e.g. User Equipments (UEs), mobile terminals, wireless terminals and mobile stations (MSs). Wireless devices are enabled to communicate wirelessly in a cellular communication network, wireless communication network or wireless communication system, sometimes also referred to as a cellular radio system or a cellular network. The communication may be performed, e.g., between two wireless devices, between a wireless device and a regular telephone and/or between a wireless device and a server via a Radio Access Network (RAN), and possibly one or more core networks, comprised within the cellular communication network.
Wireless devices may further be referred to as mobile telephones, cellular telephones, laptops, or tablet computer with wireless capability, just to mention some further examples. The wireless devices in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the RAN, with another entity, such as another terminal or a server.
The cellular communication network covers a geographical area which is divided into cell areas, wherein each cell area being served by an access node such as a base station (BS), e.g., a Radio Base Station (RBS), which sometimes may be referred to as e.g. NodeB (NB), evolved Node B (eNB or eNodeB), NodeB, B node, node B or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as, e.g., macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated on the base station site, may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the terminals within range of the base stations.
In some RANs, several base stations may be connected, e.g. by landlines or microwave, to a radio network controller, e.g. a Radio Network Controller (RNC) in Universal Mobile Telecommunications System (UMTS), and/or to each other. The radio network controller, also sometimes termed a Base Station Controller (BSC) e.g. in GSM, may supervise and coordinate various activities of the plural base stations connected thereto. GSM is an abbreviation for Global System for Mobile Communications (originally: Groupe Spécial Mobile).
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs, eNBs or even NBs, may be directly connected to other base stations and may be directly connected to one or more core networks.
The 3GPP LTE radio access standard has been written in order to support high bitrates and low latency both for uplink and downlink traffic. All data transmission is in LTE are controlled by the base stations.
UMTS is a third generation mobile communication system, which may be referred to as 3G, and which evolved from the GSM, and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for wireless devices. High Speed Packet Access (HSPA) is an amalgamation of two mobile telephony protocols, High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), defined by 3GPP, that extends and improves the performance of existing 3rd generation mobile telecommunication networks utilizing the WCDMA. Moreover, the 3GPP has undertaken to evolve further the UTRAN and GSM based radio access network technologies, for example into evolved UTRAN (E-UTRAN) used in LTE.
In the context of this disclosure, the expression Downlink (DL) may be used for the transmission path, or send direction, from a base station to a wireless device. The expression Uplink (UL) may be used for the transmission path, or send direction, in the opposite direction, i.e. from a wireless device to a base station.
An LTE RAN is currently capable of setting up and maintaining a peer-to-peer interface, named X2, between pairs of eNBs, see e.g. TS 36.300, version 12.3.0, overall architecture chapter 4. X2 is based on SCTP, see e.g. TS 36.420, version 12.0.0, chapter 6.4, “X2 interface protocol structure” and its procedures are defined by a specific protocol, X2 Application Protocol (X2AP), see e.g. TS 36.423, version 12.3.0 and chapter 8.3.3 “X2 Setup procedure”. It is currently possible for an eNB to autonomously set up X2 to another eNB when there is a need to execute procedures, for example mobility, configuration and coordination of parameters.
Until recently, the need to efficiently remove an X2 interface between two eNBs was not considered as worthy of any attention, especially in the standards. As for example stated in a document submitted to RAN3#85bis by Deutsche Telecom AG, 3GPP R3-142412, “Correction X2 interface maintenance procedures”: “While in the early times of LTE development, the automatic set up of interfaces had priority, now operator are right in the phase to maintain already deployed and set up networks in an efficient way. Operators are facing operational problems in context of maintaining X2 relations, in their continuously growing networks.”
Hence, operators may need to be able quickly and permanently remove an existing X2 interface, e.g. to reconfigure the underlying transport network, or to perform maintenance, etc., and to make sure the other peer eNB does not attempt to retry setup. In fact, many implementations may perceive the “manual” removal of an underlying Stream Control Transmission Protocol (SCTP) connection as a temporary connection failure and therefore attempt to set up X2 again to the same peer, causing additional manual intervention, unwanted signaling and potential outage.
Present solutions for removal, or release, of an X2 interface comprise:                Act via Operation And Maintenance (OAM) on both eNBs simultaneously and remove the X2 relation. This requires manual intervention on each eNB and may require a certain degree of synchronization as well as some flexibility from the eNB implementation, For example, if the other end perceives that the X2 relation is unavailable, e.g. due to the absence of SCTP connection, before it has received the new OAM setting, it may interpret this as a temporary connection failure and it may unnecessarily trigger a new X2 setup. See e.g. the above mentioned document 3GPP R3-142412, “Correction X2 interface maintenance procedures”.        Set the “No X2” flag in the Neighbor Relationship Table (NRT), see e.g. 3GPP TS 36.300, version 12.3.0, section 22.3.2. This also requires OAM intervention on both eNBs. For example, if done on only one eNB, the other will keep retrying and be rejected until some additional action by the operator.        Use a new dedicated Class 1 procedure, e.g. the one named X2 Removal as proposed in the above mentioned document R3-142412, “Correction X2 interface maintenance procedures”. However a whole new procedure requires relative complex implementation.        
Furthermore, for all the solutions above there is no way to prevent the target eNB from retrying to set up X2, i.e. there is no way to signal that a desired removal of X2 shall be permanent.